net_sched: remove qdisc_tree_flush_backlog()

This function is no longer used after the four prior fixes.

Given all prior uses were wrong, it seems better to remove it.

Signed-off-by: Eric Dumazet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: edumazet

include/net/sch_generic.h

@@ -973,14 +973,6 @@ static inline void qdisc_qstats_qlen_backlog(struct Qdisc *sch,  __u32 *qlen,
 	*backlog = qstats.backlog;
 }
 
-static inline void qdisc_tree_flush_backlog(struct Qdisc *sch)
-{
-	__u32 qlen, backlog;
-
-	qdisc_qstats_qlen_backlog(sch, &qlen, &backlog);
-	qdisc_tree_reduce_backlog(sch, qlen, backlog);
-}
-
 static inline void qdisc_purge_queue(struct Qdisc *sch)
 {
 	__u32 qlen, backlog;